Summary Rat research models are established to investigate a broad spectrum of human health issues significant to most NIH Institutes and are reported in >1.5 million publications listed on NCBI PubMed Central. Direct germline editing products and services generated by this SBIR project will streamline production of the most sophisticated, genetically designed rat models used to study gene, cell and organ function. Robust gene targeting by homology directed DNA repair in potent rat spermatogonial stem cell lines embodies technology GenomeDesigns Laboratory, LLC. (GDL) uses to introduce custom designed genomic modifications directly into the rat?s germline. Genetically modified rat germlines are transplanted into rat testes to produce fertilization-competent spermatozoa. Genetically engineered donor germline-derived spermatozoa then sexually transmit targeted alleles by breeding to generate new rat strains that harbor heritable genomic modifications needed to investigate leading biomedical questions. Phase I experiments have demonstrated feasibility to: 1) derive functionally robust, genetically tractable rat spermatogonial lines from diverse rat genetic backgrounds, 2) predict donor germline transmission rates prior to animal production, and 3) sexually transmit donor germline alleles on diverse rat genetic backgrounds from male-sterile recipients. Phase II will deliver Carrier Sperm Technology, Gene Sculptor Sperm Technology and Tissue Tracker Germlines into the model organism market. Carrier Sperm and Gene Sculptor Sperm technologies will establish spermiogenetic services exclusively offered by GDL for generating rat models that sexually transmit relatively large, allele-specific, targeted germline genomic insertions. Tissue Tracker Germlines will provide novel services for producing rat models with inducible gene regulation in target cell types of interest. Thus, Phase II deliverables will empower research requiring highly controlled, tissue-dependent and/or inducible transgene regulation using a wide assortment of inbred and outbred rat strains. Benchmarks for this Phase II SBIR project are: Specific Aim 1: Standardize Carrier Sperm Technology for transgenesis in popular rat strains Specific Aim 2: Launch Gene Sculptor Sperm services for in germline selectable marker auto-excision Specific Aim 3: Produce Tissue Tracker Germlines for inducible transgene regulation in rats